Please see the pendent sprinkler installation detail. According to NFPA 13 - 8.15.19 Return Bends tell us "22.214.171.124 Unless the requirements of 126.96.36.199, 188.8.131.52, or 184.108.40.206 are met, return bends shall be used where pendent sprinklers are supplied from a raw water source, a mill pond, or open-top reservoirs. 220.127.116.11 Return bends shall be connected to the top of branch lines in order to avoid accumulation of sediment in the drop nipples in accordance with Figure 18.104.22.168."
Raw water definition in NFPA 13; "3.3.19* Raw Water Source. A water supply that has not been treated and could contain foreign material that could enter the sprinkler system. A.3.3.19 Raw Water Source. Examples of raw water sources are mill ponds, lakes, streams, open-top reservoirs, and so forth. Examples of non-raw water sources can include city water supplies, cisterns, pressure tanks, gravity tanks, break tanks, aquifers, and so forth. Water sources that are closed or protected from direct contact with the environment should not be considered raw."
My question is I have treated city water supply so do I have to apply return bends? Is there any another information or drawing in NFPA 13?